Ultrasonic method for detecting air zone defects in a room

Abstract

One aspect of the invention relates to an ultrasonic method for detecting air zone defects in a part to be inspected, comprising: receiving an ultrasonic map of the part to be inspected; receiving a thickness map of at least a portion of the part to be inspected; determining, from the thickness map, a simulated ultrasonic map of a part without air zone defects having the same composition and thickness map as the part to be inspected; determining, from the ultrasonic map of the part to be inspected and the simulated ultrasonic map, a detection map of the part to be inspected; determining, from the detection map, the presence or absence of an air zone defect in the part to be inspected. Figure to be published with the abstract: Figure 3

Description

Title of the invention: Ultrasonic method for detecting air gap defects in a room. TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of the non-destructive testing of a part by ultrasound, and in particular by analysis of the attenuation of ultrasonic waves in the part to be tested.

[0002] The invention thus relates to an ultrasonic method for detecting defects using thickness data from at least a part of the part. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] In industry, some parts are manufactured from digital models. However, during the manufacturing process, there may be differences in structure or composition between the digital model of the part (which represents the "ideal" part that one wishes to manufacture) and the part actually manufactured. For example, for parts made of woven composite material, there may be a difference between the weave of the manufactured part and the theoretical weave supplied to the loom. These differences are not necessarily problematic and do not always need to be detected.

[0004] The manufactured part may also have defects such as cracks, fissures, delamination, or delamination (in the case of bonded materials), which result in the presence of "air pockets" within the part. Such defects alter the mechanical properties of the part and weaken it, and must therefore be detected.

[0005] To detect "air zone" type defects, ultrasonic testing methods are known to be used. In ultrasonic testing methods, ultrasonic waves are emitted by a transducer placed on the surface of the part to be inspected and propagate within it. When an ultrasonic wave encounters an interface separating two areas with different acoustic impedances in the part (in particular when the ultrasonic wave encounters a defect inside the part), part of the ultrasonic wave is reflected and the unreflected portion is attenuated.

[0006] There are classically two categories in ultrasonic testing methods: reflection methods and transmission methods (also called attenuation methods). In reflection methods, the same transducer performs both the emission of ultrasonic waves and the reception of reflected waves (i.e., "echoes" or "return signals" from the emitted waves). From the intensities and the By determining the arrival time of the return signals, it is then possible to extract information regarding the presence and location of defects in the part. In transmission methods, a receiver separate from the transmitter and placed on another surface of the part (for example, a surface opposite to the surface on which the transducer emitting the ultrasonic waves is located) receives the attenuated ultrasonic waves. Defect detection is performed based on the quantity of waves that have reached the second surface after passing through the part (only once, therefore, compared to twice – both ways – for reflection methods).

[0007] Since air zone type defects strongly attenuate ultrasonic waves, transmission methods are well suited to the detection of such defects.

[0008] For example, it is known to use such methods for parts obtained by bonding, such as aeronautical parts comprising a composite material portion onto which a metal reinforcement is bonded. An example of such parts is the LEAP engine's composite fan blade, onto which a titanium reinforcement is bonded. In the bonded areas, there may be anomalies such as porosity or lack of adhesive, which are air-zone defects. Ultrasonic testing is typically performed on the manufactured part to verify that such defects are not present.

[0009] The 3D weave of the composite material strongly disperses ultrasonic waves. In addition, the resin in the composite material strongly attenuates ultrasonic waves. For these reasons, a reflection method is very complicated to implement, and it is preferable to use an attenuation method.

[0010] The result of the ultrasonic inspection can be represented using a type C visualization, known as a "C-scan," which is a map linking the amplitude of the signal transmitted through the part to an inspection position for the surface of the inspected area. The C-scan thus provides a plan and top view of the part.

[0011] Defects are not always easily visible in the C-scan of the manufactured part, and generally, C-scan processing is implemented to highlight them. In particular, it is possible to use a reference part, which is a part of the same type as the part to be inspected (for example, a composite blade with a bonded titanium leading edge having predefined dimensions), known to be free of air zone defects. A C-scan map of this reference part is determined and used as the reference map of the part.

[0012] For each part to be inspected, a C-scan map is determined and this map is subtracted from the reference map. The result of this subtraction is a "processed" map on which the defects appear, along with other image patterns. The image is then thresholded to remove patterns other than the defects, so that only the defects remain apparent in the image is thus thresholded. The threshold used for image thresholding is a predefined threshold, which can optionally be readjusted as described below.

[0013] Defect detection according to the above method is shown in Figures 1a - 1e. In particular, Figures 1a - 1e represent a part 101 to be inspected. In this example, the part 101 shown in [Fig. 1a] is a fan blade made of composite material having a titanium leading edge 101b bonded to a body 101a made of composite material. [Fig. 1b] shows a C-scan map 102 of the part 101. This map is conventionally obtained using an attenuation-based ultrasonic inspection method. The C-scan map 102 comprises several zones 102a, 102b, 102c, 102d which correspond to different ultrasonic attenuation values.

[0014] Figure 11 represents a C-scan 103 map of a reference part. The reference part corresponds to a part of the same type as the part to be inspected 101 (for example, manufactured from the same digital model, and therefore theoretically possessing the same dimensions, structure, and components), but which is known to be free of the type of defects that are being sought in the part to be inspected 101. In other words, the reference part is an "ideal" and defect-free part. In the example in Figures 1a-1e, the reference part is an assembled blade consisting of a perfectly sound, pre-machined composite body and a bonded titanium leading edge with a geometry as close as possible to the nominal geometry. The bonding process has been previously controlled and inspected to ensure that it is free of defects.

[0015] Similar to the C-scan map 102 of the part to be inspected, the C-scan map 103 of the reference part has several zones 103a, 103b, 103c, 103d which correspond to different ultrasonic attenuation values.

[0016] Figure [11d] represents a processed map 104 obtained by subtracting the C-scan map 103 of the reference part from the C-scan map 102 of the part to be inspected. As shown in Figure [11d], the map 104 exhibits an overall narrower range of variation in ultrasonic attenuation values ​​than the C-scan maps 102 and 103. However, the processed map 104 includes areas 104a, 104b, and 104c referred to as "ultrasonic indications," which correspond to peak areas of attenuation values ​​and may represent air-type defects. To identify such defects, a thresholding can then be applied to the processed map 104 to obtain the thresholded map 105 of Figure [11d]. In other words, a threshold is applied to the attenuation values ​​of the processed map 104. In particular, this threshold can be defined as a percentage of the maximum amplitude of the received signal (i.e.Amplitudes below this percentage of the maximum amplitude are "cut off"). For example, the threshold can be a predefined value, which corresponds, for example, to an at. Signal attenuation equal to -6 dB. In other words, differences between the C-scan map 102 of the part to be inspected and the C-scan map 103 of the reference part are considered air zone defects (specifically bonding defects) when they correspond to an attenuation exceeding -6 dB. As described below, this threshold can be determined in a detailed step below. In the example of the thresholded map 105, a defect 105a appears.

[0017] The subtraction of a C-scan 103 map of a reference part from the C-scan 102 map of the part to be checked therefore makes it possible to overcome the complex geometry and the difference in thickness of the part, and thus a better detectability of defects of the type of air zones.

[0018] The threshold to be applied to the processed mapping 104 can be determined or adjusted in a further step, using a so-called "defect part." This part is of the same type as the part to be inspected, but it contains "controlled" defects, in the sense that the location, dimensions, and type of defect are known for each defect in the defect part. The defect part is typically obtained from a reference part (i.e., without defects) into which elements have been inserted that behave similarly to air-zone defects. For example, Teflon elements can be inserted, knowing that a Teflon element behaves overall similarly to an air bubble with respect to ultrasonic signals (the signals are attenuated in approximately the same way when passing through a Teflon element and when passing through an air bubble or an air gap).This defect-based part allows the threshold to be defined, for example in decibels (dB), according to tolerances relative to the actual size of the defects. In other words, since the positions of the defects in the part are known, it is possible to adjust the detection threshold to obtain the best compromise between "false positives" (detections on the thresholded map that do not correspond to a defect that one is trying to control) and "false negatives" (no element appears on the thresholded map even though there is a defect).

[0019] A flowchart of the method for detecting defects in a part according to the prior art described above is shown in [Fig.2].

[0020] In step 210, a C-scan map of a defect-free reference part (C-scan map 103 in Figures 1a-1e), also called a "gain correction vane," is obtained. In step 220, a C-scan map of the part to be inspected (C-scan map 102 in Figures 1a-1e) is obtained. The C-scan map of the (defect-free) reference part is subtracted (step 230) from the C-scan map of the part to be inspected to obtain a so-called processed map (map 104 in Figures 1a-1e).

[0021] During step 240, a C-scan mapping of the defective part (the defects being known, as detailed above) is obtained, and used to determine an optimal threshold (step 250) for detecting defects, as described above.

[0022] During a step 260, the threshold determined in step 250 can be applied to the processed map obtained in step 230. The defect(s) can then be identified in the thresholded map during a step 270. Indeed, the deviations between the part to be inspected and the defect-free reference part, which are "ultrasonic indications", should theoretically only be bonding anomalies, i.e. air zone type defects.

[0023] The C-scan mapping of the reference part, the C-scan mapping of the part to be inspected and the C-scan mapping of the defective part are typically obtained by a transmission ultrasonic inspection method.

[0024] It is noted that steps 210, 220 and 240 can be carried out in parallel or in any order (although in general, steps 210 and 240 on the reference part and the defective part are carried out before carrying out the actual inspection of a part, therefore before step 220).

[0025] In the prior art process described above, the role of the defect-free reference part is to obtain a processed C-scan map that is as homogeneous as possible, which is free from the attenuation variabilities induced by the material(s) used and the thicknesses of the part (in particular the composite material and / or the thicknesses of the different materials such as titanium in the previous example).

[0026] However, the defects that one seeks to detect are not the only ones to generate ultrasonic indications, i.e., areas of ultrasonic attenuation peaks. Other factors can generate ultrasonic indications, notably the variability in the structure or thickness of the part (in the case of the composite blade with a bonded titanium leading edge, for example, the variability in the geometry of the leading edge and / or the variability in the woven weave generate such ultrasonic indications). These unanticipated variabilities at the implementation of the inspection can arise, for example, from the diversity of suppliers for the same product, changes in geometries, the manufacturing process, and / or the broadening of the geometric acceptance criteria on the part (or intermediate parts, i.e., the leading edge and the pre-machined body in the previous example).These variabilities give rise to false positives (false defects) detected on the mapping after thresholding.

[0027] One solution would be to adapt the threshold to the different parts of the part to be inspected, but such a solution is difficult to implement because it requires, beforehand, determining the areas in which variability in attenuation is acceptable, and determining the associated acceptability threshold. This solution also presents the risk of increasing the number of false negatives, that is, the number of undetected defects (particularly because they are located in a part of the part for which it was (considering that greater variability in attenuation is acceptable).

[0028] There is therefore a need to improve the detection of air zone type defects in parts and to get rid of irrelevant ultrasonic indications (i.e. of zones which appear on the thresholded map as defects when they are not). Summary of the invention

[0029] The invention offers a solution to the problems mentioned above by using thickness data from the manufactured part to be inspected to construct a simulated ultrasonic map of a virtual part, and using this simulated ultrasonic map as a reference map (instead of the ultrasonic map of a defect-free reference part, as in the prior art method described above). The use of such a simulated ultrasonic map reduces irrelevant ultrasonic readings due, in particular, to variability in the geometry of the manufactured part compared to the digital model on which it is based.

[0030] One aspect of the invention relates to a computer-implemented method for detecting air zone defects in a part to be inspected using ultrasound. The method comprises:

[0031] - receive an ultrasonic map of the part to be checked;

[0032] - receive a thickness map of at least a portion of the part to to control;

[0033] - determine, from the thickness mapping of at least a portion of the part to be inspected, a simulated ultrasonic mapping of at least a portion of a part without air zone defects having the same composition and thickness mapping as at least a portion of the part to be inspected;

[0034] - determine, from the ultrasonic mapping of the part to be inspected and the simulated ultrasonic mapping, a detection mapping of the part to be inspected;

[0035] - determine, by applying a predefined threshold to the detection mapping of the part to be checked, presence or absence of an air zone type defect in the part to be checked.

[0036] By "air zone defect" is meant a defect in the part whose behavior with respect to ultrasound (in particular the ultrasonic attenuation coefficient) is similar to that of an air zone present in the part. When ultrasonic waves have such a defect, they are typically attenuated more than when they pass through the rest of the part. Such a defect could be, for example, an air bubble or a crack.

[0037] The term "part to be inspected" refers to the mechanical part in which the possible presence of a defect is sought. It should be noted that the method can be applied to a complete part or to a portion of a part (rather than a complete part), both referred to hereafter as "part" or "part to be inspected" for the sake of simplicity.

[0038] By "ultrasonic mapping," we mean a graphical representation of the ultrasonic behavior at different points in the part. For example, the ultrasonic map can be a 2D image of a projection of the part onto a predefined plane, representing the amplitudes of ultrasonic signals at the different points of the projection after passing through the part. In particular, each point of the map can be associated with data relating to the ultrasonic behavior of the part along an axis passing through the point in question in a direction orthogonal to the projection plane. For example, the data relating to this can be an amplitude value of the signal exiting the part, which reflects the attenuation experienced by the ultrasonic wave as it passes through the part. Since air zone defects attenuate the ultrasonic signals passing through them, these attenuations are visible in the ultrasonic map of the part.

[0039] The “ultrasonic mapping of the part to be checked” is therefore a mapping obtained on the complete part (or portion of part), after its manufacture.

[0040] By "thickness map," we mean a graphical representation of the thickness of the part along a given direction. Typically, the thickness map represents a projection of the part onto the same plane as the ultrasonic map, in which each point of the projection is associated with a value representing the thickness of the part at that point, along the direction orthogonal to the plane in question. For example, the thickness map can be a 2D image comprising a plurality of pixels, each pixel having a value calculated based on the thickness of the part at a point corresponding to the pixel in question.

[0041] Depending on the method, the received thickness map is either a thickness map of the entire part to be inspected or a thickness map of only a portion of the part to be inspected. For example, when the part to be inspected is an engine blade comprising a body made of composite material and a titanium leading edge bonded together, the received thickness map may be a map of the leading edge only. Conversely, the received ultrasonic map is an ultrasonic map of the entire part.

[0042] By "simulated ultrasonic mapping" of the part or portion of the part, it is understood that a mapping which "simulates" an ultrasonic mapping of the part or portion of the part, but which has not been established (at least in part) from an ultrasonic method applied to the part to be inspected or to the portion of the part to be inspected. control. More precisely, the simulated ultrasonic map is determined here from the thickness map. In other words, the thickness map is "transformed" into an equivalent ultrasonic map, which would theoretically be obtained if an ultrasonic method were applied to the part or portion of the part to study its ultrasonic behavior and deduce an ultrasonic map, assuming that this part or portion of the part does not contain any defects.

[0043] The simulated ultrasonic mapping corresponds to the ultrasonic mapping of a "virtual" part that would be similar to the part under consideration and that would not have any air zone defects. The underlying idea is that, in the absence of defects, the attenuation of ultrasonic waves depends on an average attenuation coefficient of the medium through which they pass and the length traveled by the ultrasonic signals (and therefore on the thickness of the part). By using attenuation data for parts corresponding to the same medium (which may be heterogeneous, for example, several media successively traversed) and the actual thickness data of the part (i.e., the true thickness of the manufactured part, incorporating its possible variations relative to the digital model according to which it was manufactured), it is possible to deduce a simulated ultrasonic mapping of a part having the same thickness mapping, but which would not have any defects.Simulated ultrasonic mapping thus makes it possible to obtain a reference map of ultrasonic behavior in the room in the absence of defects.

[0044] By "composition," we mean a set of parameters defining the structure and the material(s) constituting the part (or portion of a part). For example, for a part made of woven composite material, the composition includes, in particular, the type of weave, the type of warp and weft yarns, the warp / weft ratio, etc. By "a defect-free part having the same composition and thickness mapping" as the part to be inspected, we therefore mean a virtual part that is "identical" in terms of composition and dimensions to the part to be inspected, but which is assumed to be free of air zone defects.

[0045] By "detection map," we mean a representation of a projection of the part on which any potential defects are determined. In the present process, this detection map is obtained from the (actual) ultrasonic map of the manufactured part and the simulated ultrasonic map (which serves as a reference).

[0046] The above method advantageously uses the actual thickness data of the part to be inspected to construct an ultrasonic (simulated) map that serves as a reference for determining the presence or absence of air zone defects. The method is thus more precise than the traditional prior art method described above, in which the reference map is derived from an "ideal" (physical) part, which may exhibit differences in thickness compared to the part being inspected.

[0047] In one or more embodiments, the detection map of the part to be inspected may comprise a plurality of pixels, each pixel among the plurality of pixels being associated with a respective value. Determining the presence or absence of an air zone defect in the part to be inspected may include:

[0048] - determining whether there is a group of neighboring pixels in the detection map of the part to be checked for which the values ​​associated with the pixels of said group are less than or greater than the predefined threshold:

[0049] if there is a group of neighboring pixels in the detection map of the part to be checked for which the values ​​associated with the pixels of said group are less than or greater than the predefined threshold, detect an air zone type defect;

[0050] if there is no group of neighboring pixels in the detection map of the part to be checked for which the values ​​associated with the pixels of said group are less than or greater than the predefined threshold, detect an absence of air zone type defects.

[0051] According to these embodiments, the detection map is an image comprising a plurality of pixels, each pixel being associated with a respective value. The value associated with a pixel may be, for example, a gray level or a light intensity value. It is understood that the invention is not limited to a single value per pixel; for example, each pixel may be associated with a triplet of values ​​representing the intensity values ​​on the three red, green, and blue channels of the pixel.

[0052] By "neighboring pixels" is meant pixels connected to each other by a connection relationship, for example, a 4-connectivity relationship. By "group of neighboring pixels" is meant that each pixel in the group is a neighbor of at least one other pixel in the group. The group of pixels may comprise a single pixel or more than two pixels. In some embodiments, a condition may be added on the number of pixels forming the group (thus, a set of neighboring pixels is considered a "group" in the above sense if it comprises a number of pixels greater than or equal to a predefined lower limit).

[0053] According to the embodiment, the pixel groups may include pixels whose values ​​are above the predefined threshold or pixels whose values ​​are below the predefined threshold. These embodiments are equivalent.

[0054] When the pixel values ​​of the detection map are greater (or less) than the predefined threshold, this means that the signals have been more strongly attenuated when passing through the part, which may indicate the presence of a defect.

[0055] In some embodiments, the thickness mapping can be a thickness map of the entire part. The thickness map of the part to be inspected can comprise a plurality of pixels, each pixel of the plurality of pixels being associated with a respective value, and the simulated ultrasonic mapping can be determined by applying a transformation to the pixel values ​​of the thickness map of the part to be controlled.

[0056] According to these embodiments, the thickness mapping is therefore performed on the entire part (and not on a portion of the part). The thickness map is "transformed" into a simulated ultrasonic map, which is therefore the ultrasonic map that a part similar to the part to be inspected would have in the absence of a defect.

[0057] In some embodiments, the method may further comprise:

[0058] - realign the thickness map of the part to be checked with the ul map trasonore of the room to be checked;

[0059] and the transformation can be applied to the thickness mapping of the re-marked part.

[0060] By "registration," it is understood that pixels from the two maps corresponding to the same points in the projection of the part are matched. This allows the respective information from the maps to be combined.

[0061] According to these embodiments, the registration is applied before transforming the thickness map to obtain the simulated ultrasonic map.

[0062] Alternatively, the method may further comprise:

[0063] - recalibrate the simulated ultrasonic mapping of the room with the ultrasonic mapping trasonore of the piece;

[0064] and the detection mapping can be determined from the ultrasonic mapping of the part and the simulated and recalibrated ultrasonic mapping of the part.

[0065] According to these embodiments, the recalibration is applied after the transformation, on the simulated ultrasonic mapping.

[0066] In alternative embodiments, the part to be inspected comprises a first part and a second part bonded together, the second part being manufactured according to a predefined digital model. The thickness mapping may be a thickness map of the first part of the part to be inspected before assembly with the second part of the part to be inspected, and the ultrasonic mapping of the part to be inspected may be an ultrasonic map of the assembled part to be inspected. The method may further include:

[0067] - receive a reference ultrasonic mapping of the second part of the piece to be checked, the reference ultrasonic mapping of the second part of the part to be checked corresponding to an ultrasonic mapping of a second reference part manufactured from the predefined digital model and not including any air zone type defects;

[0068] and the simulated ultrasonic mapping can be determined from the thickness mapping of the first part of the part to be controlled and the reference ultrasonic mapping of the second part of the part to be controlled.

[0069] According to these embodiments, the part to be inspected comprises at least two parts bonded together. The bonding area may typically contain defects such as air pockets, for example, due to insufficient adhesive or an air bubble in the adhesive. Ultrasonic mapping is always performed on the complete (and assembled) part. In contrast, thickness mapping only concerns the first part of the part, before it is bonded to the second part. In these embodiments, a so-called "reference" ultrasonic map of the second part is also obtained.This reference ultrasonic mapping of the second part of the part is typically an ultrasonic mapping performed on a second part of the part "similar" to the second part of the part being inspected, but which is known to be free of defects (as was the case in the prior art method on the whole part; conversely, here it only concerns the second part of the part).

[0070] Such embodiments are particularly advantageous when the part comprises a portion whose thickness varies very little, and a portion whose thickness varies more.

[0071] In these embodiments, the thickness map of the first part of the part to be inspected may comprise a plurality of pixels, each pixel of the plurality of pixels being associated with a respective value. The method may further comprise:

[0072] - applying a transformation to the plurality of pixels of the thickness map of the first part of the part to be checked;

[0073] in which the simulated ultrasonic mapping can be determined from the reference ultrasonic mapping of the second part of the part to be controlled and the transformed thickness mapping of the first part of the part to be controlled.

[0074] The thickness map of the first part of the part is thus transformed into an equivalent ultrasonic map in the absence of defects, and the simulated ultrasonic map is determined by "grouping" the reference ultrasonic map of the second part and the equivalent ultrasonic map obtained for the first part.

[0075] In some embodiments, the process may further comprise:

[0076] - realign the thickness mapping of the first part of the part and the car ultrasonic tography of the second part of the room with ultrasonic mapping of the room;

[0077] wherein the transformation can be applied to the thickness mapping of the reworked part; and

[0078] wherein the simulated ultrasonic mapping of the part can be obtained by summing the ultrasonic mapping of the second part of the rejected part and the mapping obtained by applying the transformation to the thickness mapping of The rejected part.

[0079] Alternatively, the method may further include:

[0080] - to realign the mapping obtained by applying the transformation to the car thickness tography of the rejected part and ultrasonic mapping of the second part of the part with the ultrasonic mapping of the part;

[0081] in which the simulated ultrasonic mapping of the part can be obtained by summing the ultrasonic mapping of the second part of the re-marked part and the mapping obtained by applying the transformation to the thickness mapping of the re-marked part.

[0082] In one or more embodiments, the transformation can be a multiplication by a predetermined coefficient.

[0083] In particular, the method may include a preliminary calculation of the predetermined coefficient. The preliminary calculation of the coefficient may include:

[0084] - for each part of a set of parts without defects of the air zone type having the same composition as the part to be checked:

[0085] receive a thickness map of said part, the thickness map comprising a plurality of pixels, each pixel being associated with a respective value;

[0086] receive an ultrasonic map of said part comprising a plurality of pixels, each pixel being associated with a respective value;

[0087] determine a ratio between pixel values ​​of the thickness mapping with corresponding pixel values ​​of the ultrasonic mapping;

[0088] - calculate the coefficient from the determined ratios.

[0089] In embodiments, the detection map is obtained by subtracting the ultrasonic map of the part to be controlled from the simulated ultrasonic map.

[0090] For example, the part may be an aeronautical part. In particular, in the case where the part comprises two parts, the part may be an engine blade, in which the first part of the part is a metal leading edge, and in which the second part of the part is a body made of woven composite material.

[0091] In embodiments, the air zone type defect may be the presence of a crack, fissure, delamination or delamination.

[0092] In some embodiments, the maps are type C visualizations.

[0093] Another aspect of the invention relates to an ultrasonic detection device for Air zone defects in a room to be monitored. The device may include:

[0094] - an input interface configured for:

[0095] receive an ultrasonic map of the part to be inspected;

[0096] receive a thickness map of at least a portion of the part to be checked;

[0097] - a circuit configured for:

[0098] determine, from the thickness mapping of at least one portion of the part to be checked, a simulated ultrasonic mapping of at least one portion of a part without air zone type defects having the same composition and the same thickness mapping as the at least one portion of the part to be checked;

[0099] determine, from the ultrasonic mapping of the part to be inspected and the simulated ultrasonic mapping, a detection map of the part to be inspected;

[0100] determine, by applying a predefined threshold to the detection mapping of the part to be inspected, the presence or absence of an air zone type defect in the part to be inspected.

[0101] A computer program, implementing all or part of the process described above, installed on pre-existing equipment, is in itself advantageous.

[0102] Thus, the present invention also relates to a computer program comprising instructions for the implementation of certain steps of the process described above, when this program is executed by a processor.

[0103] This program may use any programming language (for example, an object-oriented language or other), and may be in the form of interpretable source code, partially compiled code or fully compiled code.

[0104] The [Fig.3] described in detail below can form the flowchart of the general algorithm of such a computer program.

[0105] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0106] Other features and advantages of the invention will become apparent from the description, which can be read in conjunction with the figures. These figures are provided for illustrative purposes only and are not intended to limit the scope of the invention.

[0107] [Fig.la], [Fig.lb], [Fig.le], [Fig.ld], [Fig.le] Figures la to le illustrate certain steps of a prior art method for detecting air zone defects.

[0108] [Fig.2] Fig.2 represents a flowchart of a method for detecting air zone type defects according to the prior art.

[0109] [Fig.3] Fig.3 represents a flowchart of a method for detecting air zone type defects according to an embodiment of the invention.

[0110] [Fig.4] The [Fig.4] represents a flowchart of a method for detecting defects of the air zone type according to another embodiment of the invention. [YES] [Fig.5a], [Fig.5b], [Fig.5c] Figures 5a, 5b and 5c illustrate a step in determining a simulated ultrasonic map of the part according to an embodiment of the invention.

[0112] [Fig.6] Fig.6 represents a flowchart of a detection method for air zone type defects incorporating a determination of the threshold to be applied according to embodiments of the invention.

[0113] [Fig.7] The [Fig.7] represents an example of an air zone type defect detection device according to embodiments of the invention. DETAILED DESCRIPTION

[0114] Fig. 3 represents a flowchart of a method for detecting air zone defects according to an embodiment of the invention.

[0115] According to this embodiment, the part is considered as a whole (whereas in the embodiment described with reference to [Fig.4], it is considered as an assembly of two parts glued together).

[0116] In a step 220 similar to that described with reference to [Fig. 2], an ultrasonic map, for example a C-scan map, of the room is received. The ultrasonic map of the room is typically an image comprising a plurality of pixels, in which each pixel is associated with a light intensity value that represents an amplitude of the received signal (or equivalently, an attenuation value of the ultrasonic signal as it propagates through the room, also called the ultrasonic attenuation value) in the region of the room corresponding to that pixel. In other words, each pixel reflects how the emitted ultrasonic signal is attenuated as it propagates through the room. Thus, pixels corresponding to areas of the room containing air-zone defects are generally associated with light intensity values ​​reflecting greater ultrasonic attenuation of the signal.

[0117] In step 310, a thickness map of the part is obtained. The thickness map of the part is typically an image comprising a plurality of pixels, in which each pixel is associated with a light intensity value that represents a thickness of the part along a given direction. For example, if the part is in an (X, Y, Z) coordinate system, a map of the part along the Z-axis represents the thickness of the part along the Z-axis, shown in the (X, Y) plane.

[0118] Thickness mapping can be obtained, for example, using a prior art dimensional control method. For example, thickness mapping can be established from measurement data obtained using a coordinate measuring machine (CMM). Such a machine makes it possible, using probes and / or optical sensors moved by a measuring arm, to determine the dimensions, shape, and position of the object being measured in a given coordinate system, and therefore the thicknesses of this object in several directions. The measured data can then be processed, for example, by metrology software that allows for the modeling of the object as well as the detection of dimensional deviations of the part relative to the digital model according to which it was manufactured.

[0119] The ultrasonic mapping of the received part in step 220 and the thickness mapping of the received part in step 310 are typically images of the same dimensions (i.e., having the same number of pixels along both image axes). It is noted that steps 220 and 310 can be implemented in any order, or in parallel.

[0120] In one or more embodiments, it is possible to implement a 320 registration process to align the ultrasonic mapping of the part with the thickness mapping of the part. Indeed, depending on how the two maps were obtained, they may not perfectly match. For example, a pixel corresponding to a point on the part may not have the same coordinates in both images. Typically, there may be a rotation and / or translation of one of the images relative to the other. To align the two maps and thus combine their respective information, a transformation can be applied to one of the maps to "register" it with the other map.

[0121] Such image registration techniques are known to those skilled in the art. In particular, it is possible to use a registration technique based on reference points of the part, the positions of which are known. The pixels corresponding to these reference points can be identified on each of the maps, and the transformation to be applied to perform the registration 320 can be determined from these pixels. For example, if a point M of the part is associated with pixel p with coordinates (x, y) in the ultrasonic map and with pixel p' with coordinates (x', y') in the thickness map, the transformation T to be applied is such that T(x', y') = x, y (or such that T(x, y) = (x', y')). As mentioned above, these techniques are known and are not further detailed here. An example of registration is illustrated in Figures 5a, 5b, and 5c, in a particular embodiment of the invention.

[0122] In one or more embodiments, a transformation can be applied to the thickness map of the part during a step 330 to modify the intensity values ​​of the pixels in the thickness map in order to obtain a so-called "simulated" ultrasonic map of a part similar to the part under consideration (i.e., having the same composition, structure, and dimensions) that would not exhibit any defects. At the end of step 330, a simulated ultrasonic map of the part is thus obtained. The word "simulated" here refers to the fact that the map obtained "simulates" an ultrasonic map, even though it is obtained (at least partially) from a thickness map. It is clearly noted that the word "simulated" here does not designate a map that would be entirely derived from a si- computer emulation.

[0123] For example, in step 330, it is possible to multiply the light intensity values ​​of each pixel of the thickness map by the same predefined coefficient to obtain the simulated ultrasonic map. This coefficient can be determined upstream of the detection method according to the invention, for example, from a part having several known thicknesses, for which an ultrasonic map is created. For example, it is possible to use a stepped gauge block with varying thicknesses (for example, 5 steps with thicknesses of 1 mm for the first step, 2 mm for the second step, ... and 5 mm for the fifth step, the number of steps and their respective thicknesses being provided by way of example only and in a non-limiting manner), the thickness of each step being known.Ultrasonic mapping allows for the determination of ultrasonic attenuation values ​​for each step (for example, -3 dB for the first step, -4 dB for the second step, ..., and -7 dB for the fifth step). A correlation between the thickness values ​​and the corresponding attenuation values ​​is then established. For example, a relationship of the type: Att = (Ep x n) + z is established, where Att represents the ultrasonic attenuation, Ep represents the thickness, and n and z are two parameters determined from the experimental values ​​of ultrasonic attenuation and thickness obtained on the stepped block. Models of the relationship between ultrasonic attenuation and thickness other than a linear model like the one described above are, of course, possible.

[0124] Alternatively, it is possible to define different coefficients for different regions of the part thickness map. For example, these regions may correspond to areas of the part made of different materials (and therefore with different average attenuation coefficients), and the coefficients to be applied to the pixels in each region may be determined as before.

[0125] Other methods for determining the coefficient(s) can be implemented, for example, machine learning methods. For example, a machine learning model can be trained on a training database comprising pairs of maps, each pair comprising a thickness map of a part and an ultrasonic map of the same part, to determine, from a thickness map, the coefficient(s) to be applied to obtain the "equivalent" ultrasonic map. Such a model could be, for example, a neural network, in particular a GAN (Generative Adversarial Network), but the invention is not limited to this example.

[0126] At the end of step 330, the simulated ultrasonic mapping is “similar” to an ultrasonic map, in the sense that the light intensity value of a pixel of The simulated ultrasonic mapping is at least approximately equal to a light intensity value of a pixel corresponding to the same point in the ultrasonic map. In other words, the applied transformation allows thickness values ​​to be converted into equivalent ultrasonic attenuation values.

[0127] The transformation applied in step 330 advantageously allows the light intensity values ​​of the ultrasonic mapping and the thickness mapping to be sufficiently comparable, so that the information from these two maps can be combined.

[0128] In the foregoing, step 330 was described in the case where the transformation is applied to the thickness map of the part. It is noted that alternatively, the transformation can be applied to the ultrasonic map of the part to modify the intensity values ​​of the pixels of the ultrasonic map so that they coincide with the intensity values ​​of the pixels of the thickness map of the part, in a manner similar to that described above.

[0129] In step 340, the simulated ultrasonic map determined in step 330 is subtracted from the received ultrasonic map in step 220. Alternatively, it is of course possible to subtract the ultrasonic map from the simulated ultrasonic map. By "subtraction," it is understood that a pixel-by-pixel subtraction is performed, meaning that each pixel of the subtracted image is associated with a value that corresponds to the difference between the value of the corresponding pixel (i.e., the pixel with the same coordinates) in one of the maps and the value of the corresponding pixel in the other map.

[0130] The map obtained at the end of step 340, also called the "detection map," reveals air zone defects. These zones are indeed associated with higher pixel values. This is because, in the absence of a defect, the ultrasonic attenuation values ​​are directly correlated to the thickness of the part. Conversely, if the ultrasonic signal passes through an air zone defect, it is attenuated more. For the pixels corresponding to this defect, a difference therefore appears between the values ​​of the ultrasonic map (which include the defect) and the values ​​of the thickness map (which represent values ​​"equivalent" to the attenuation values ​​of the part, without the defect).

[0131] The detection map obtained in step 340 exhibits fewer false positives (i.e., false ultrasonic indications) than the processed map obtained in step 230 of the prior art process described with reference to [Fig. 2], because it is much less subject to factors related to material variability. This detection map therefore allows for significantly more reliable detection than the prior art process described above.

[0132] Similar to the method in [Fig. 2], a thresholding 260 can be applied to the detection map obtained in step 340. In particular, it is possible to retain only the pixel values ​​above a predetermined threshold. In one or more embodiments, the threshold can be determined as described with reference to [Fig. 2] (step 250). For example, the threshold can correspond to an attenuation percentage of -6 dB.

[0133] According to one embodiment, pixels whose values ​​are above the threshold can be set to a first reference value, for example, a gray level of 0 (black pixel), and pixels whose values ​​are below the threshold can be set to a second reference value, for example, a gray level of 255 (white pixel). The thresholded detection map is then a black and white image in which the defects appear black and the background white. Alternatively, pixels whose values ​​are above the threshold can retain the same value, and pixels whose values ​​are below the threshold can be set to a reference value, for example, a gray level of 255 (white pixel). The detection map is then an image with a white background, and the defects retain their intensity values ​​calculated in step 260. Other embodiments are possible.

[0134] Similar to the method in [Fig. 2], the presence or absence of air zone defects can be determined in step 270, based on the thresholded detection map obtained in step 260. In one embodiment, zones corresponding to groups of neighboring pixels whose values ​​are all above the predefined threshold used for thresholding 260 are considered defects. "Neighboring pixels" means a set of pixels in which each pixel is connected to at least one other pixel in the set by a connection link (e.g., a 4-connectivity link). In some embodiments, it is possible to define a minimum number Nmin of pixels for each group. According to these embodiments, to be detected as corresponding to a defect, the group of neighboring pixels must include at least Nmin neighboring pixels.If there are no groups of neighboring pixels whose values ​​exceed the predefined threshold, there is no defect in the controlled room.

[0135] Figure 4 represents a flowchart of a method for detecting defects in type air zones according to another embodiment of the invention.

[0136] In this embodiment, the part to be controlled comprises two parts (a first part and a second part) intended to be joined by bonding. For example, the part to be controlled may be an engine blade comprising a body and a leading edge, the body being made of a woven composite material and the leading edge being made of metal, for example titanium. The body and the leading edge are manufactured separately and are joined by bonding to form the engine blade. In such parts, which include sections bonded together, there is a risk that the bonding process may contain defects such as air pockets (due, for example, to insufficient or absent adhesive or to porous areas), which weaken the part and must be detected. It is understood that this embodiment can be extended to a part comprising more than two sections intended to be joined by gluing (at least one section and another section).

[0137] During step 220, an ultrasonic map, for example a C-scan map, of the complete and assembled part (i.e., the parts of the part are already bonded) is received. This step is similar to step 220 described with reference to [Fig. 2] or [Fig. 3]. In the example of the motor blade above, during step 220, an ultrasonic map of the assembled blade is therefore received.

[0138] In step 302, a reference ultrasonic map, for example a C-scan, of a first part of the part is received. By "reference ultrasonic map" it is understood that the ultrasonic map is not necessarily a map of the first part of the part to be inspected, but may be an ultrasonic map of a first part of the same type as the first part of the part to be inspected.

[0139] In the example of the engine blade, the first part of the component is typically the body made of composite material. The body is conventionally manufactured from a digital reference model specific to a particular type of blade, which is the same for all blades manufactured according to that particular blade type. Thus, in step 302, a reference ultrasonic map is received of a blade body manufactured from the digital reference model associated with the blade to be inspected. Generally, the first part of the component is one whose thickness varies relatively little from one component to another (this is the case for parts made of woven composite material).

[0140] It is therefore understood that the same ultrasonic reference map of the first part of the part can be determined upstream of the control process of [Fig.4], and that it can be used to control several different parts from the same digital model specific to this type of first part of the part (i.e. that this reference map can be used for steps 302 of several control processes according to [Fig.4] applied to several parts to be controlled).

[0141] It is noted that the reference ultrasonic mapping of the first part received in step 302 is an ultrasonic mapping of a first part (for example, a reference part) before it is glued to the second part.

[0142] In step 304, a thickness map of the second part of the part to be inspected is received before it is bonded to the first part. In the example above, this is therefore the thickness map of the titanium leading edge of the part to be inspected before it is bonded to the blade body made of composite material. Indeed, in the engine blade, which comprises a bonded assembly of a woven composite body and a titanium leading edge, it is the titanium leading edge that exhibits the greatest variability in thickness from one part to another. Therefore, it is this part for which we want to determine the exact thickness of the part in question. Generally, the second part of the component is chosen as the one with the greatest variability in thickness from one part to another (and thus relative to a reference model according to which the second parts of the components are manufactured).

[0143] It is therefore noted that step 302 relates to a reference ultrasonic mapping, while step 304 relates to a thickness mapping of the second part of the part under consideration (to be checked).

[0144] The thickness mapping of the second part of the part to be controlled is typically obtained by a part thickness measurement technique as described above, with reference to step 310 of [Fig.3].

[0145] In step 325, a registration of the different maps can be carried out. This registration makes it possible to "coincide" the pixels corresponding to the same points of the part in the different maps (i.e. to put them at the same coordinates, so that all the maps correspond to the same image of the part).

[0146] An example of such a registration 325 is illustrated in Figures 5a, 5b, and 5c. Figure 5a represents an ultrasonic map 510 of the assembled part to be inspected. The crosses on the ultrasonic map 510 represent "reference" points, used to register the images relative to each other. In practice, these reference points are positioned according to physical features of the parts considered before assembly, visible on the different maps. On the ultrasonic map 510 of the assembled part to be inspected, the two parts 512 and 514 of the part appear, that is, in the example of the blade, the leading edge and the body, respectively.

[0147] Fig. 5a also represents the 520 reference ultrasonic mapping of the second part 514 of the part (here, the blade body), as well as the reference points (also represented by crosses).

[0148] The reference points of the maps 510 and 520 are matched to determine the transformation used to register the reference ultrasonic map 520 of the second part of the part to portion 514 of the ultrasonic map 510 (portion 512 is ignored for this registration step). In the illustrated case, the transformation is composed of a translation, a rotation, and a homothety. Once the transformation is determined and applied to all pixels of the reference ultrasonic map 520 of the second part of the part, a transformed reference ultrasonic map 530 of the second part of the part is obtained.

[0149] Fig. 5b shows the same ultrasonic mapping 510 of the assembled part to be inspected as Fig. 5a. Fig. 5b also shows the thickness mapping 540 of the first part of the part (here, the leading edge), as well as the reference points (also represented by crosses).

[0150] As before, the reference points of the maps 510 and 540 are matched to realign (step 325) the thickness map 540 of the first part of the part with the ultrasonic map 510 of the assembled part to be inspected. In addition, a transformation can be applied to the thickness map 540 of the first part of the part (before or after realignment) so that the light intensity levels of the pixels of the thickness map 540 of the first part of the part correspond globally to the light intensity levels of the corresponding pixels (i.e. representing the same point of the part after realignment), as detailed previously with reference to step 330 of [Fig. 3].After registration and transformation (for example, multiplying the pixel values ​​of the thickness map 540 of the first part of the part by one or more coefficients), a simulated ultrasonic map 550 of the first part of the part is obtained, registered with the ultrasonic map of the complete part 510 (more precisely, with portion 512 of the map 510).

[0151] Figure 5c represents a simulated ultrasonic map 560 of the part obtained from the transformed reference ultrasonic map 530 of the second part of the part and the simulated ultrasonic map 550 of the first part of the part. For example, this simulated ultrasonic map 560 of the complete part is obtained by summing, pixel by pixel, the maps 530 and 550. It is noted that here, the word "simulated" is used to denote the fact that the map 560 simulates an ultrasonic map even though it is partially derived from thickness data (for the first part of the part, i.e., the titanium leading edge in the previous example).

[0152] At the output of step 330, we therefore obtain a simulated ultrasonic map 560 of the part as represented by element 560 of [Fig.5c].

[0153] Steps 340, 260, and 270 of [Fig. 4] are similar to steps 340, 260, and 270 of [Fig. 3]. Thus, in step 340, a detection map is obtained by subtracting the simulated ultrasonic map determined in step 330 from the ultrasonic map received in step 220 (in either direction). Then, a threshold 260 can be applied to the detection map obtained in step 340, and the presence or absence of air zone defects can be determined in step 270 from the thresholded detection map obtained in step 260.

[0154] Figure 6 represents a flowchart of a method for detecting air zone defects, incorporating a determination of the threshold to be applied according to modes of realization of the invention.

[0155] In step 330 (which replaces step 210 of [Fig. 2]), a simulated ultrasonic map of the part is obtained. Step 330 can, for example, be implemented as described previously with reference to [Fig. 3] and [Fig. 4]. In step 220, an ultrasonic map of the part to be inspected is obtained. The simulated ultrasonic map of the part can be subtracted (step 340) from the C-scan map of the part to be inspected to obtain a detection map.

[0156] As described with reference to [Fig. 2], in step 240, a C-scan map of the defective part (the defects being known, as detailed above) is obtained and used to determine an optimal threshold (step 250) for detecting the defects, as described above. In step 260, the threshold determined in step 250 can be applied to the processed map obtained in step 340. The defect(s) can then be identified in the thresholded map in step 270.

[0157] Steps 330, 220 and 240 can be carried out in parallel or in any order (although in general, steps 330 and 240 on the reference part and the defective part are carried out before the actual inspection of a part, therefore before step 220).

[0158] The process of [Fig. 6] is therefore similar to the process of [Fig. 2], but instead of using an ultrasonic map of a reference part, the process uses a simulated ultrasonic map of the part, determined from thickness data of the manufactured part. The variability in thickness related to the manufacturing of the part (and which therefore does not necessarily indicate the presence of a defect) is thus advantageously taken into account and integrated into the detection process. The resulting detection process is therefore more precise and generates fewer false positives related to the variability in the manufacturing of the part than the prior art process described with reference to [Fig. 2].

[0159] Figure 7 represents an example of an air zone type defect detection device according to embodiments of the invention.

[0160] In these embodiments, the device includes a computer 700, comprising a memory 701 for storing instructions enabling the implementation of the process, the various maps from which the detection process is implemented, and temporary data for carrying out different steps of the detection process described above.

[0161] The computer 700 further comprises a circuit 702. This circuit may be, for example, a processor capable of interpreting instructions in the form of a computer program, an electronic card whose steps of the process of the invention are described in silicon, or a programmable electronic chip such as an FPGA chip (for "Field-Programmable Gate Array" in English).

[0162] The computer 700 includes an input interface 703 for receiving ultrasonic maps and / or thickness maps, and an output interface 704 for providing a detection map or one or more pieces of information relating to defect detections (for example, an indication of the absence or presence of defects, and / or, when a defect is detected, an indication of the defect's location). Finally, the computer may include, to allow easy interaction with a user, a screen 705 and a keyboard 706. Of course, the keyboard is optional, particularly in the case of a computer in the form of a touchscreen tablet, for example.

[0163] Furthermore, the functional diagrams shown in Figures 3 and 4 are typical examples of programs, some instructions of which can be executed using the described device. In this respect, [Fig. 3] can be considered the flowchart of the general algorithm of a computer program as defined in the invention.

[0164] Of course, the present invention is not limited to the embodiments described above by way of example. It extends to other variations. For example, the method described above is advantageously applicable in cases of ultrasonic inspection of industrial parts with complex geometries and variations in thickness that could generate false readings. Such industrial parts may include bonded or welded assemblies for which it is necessary to guarantee the quality of the bonding or welding, and in particular to determine whether they have areas of missing material, porosity, or contain foreign bodies. Such industrial parts may also include homogeneous parts subjected to a material integrity test, during which volumetric defects such as delamination or inclusions are sought.

[0165] In order to obtain equivalent inspection results and reliable detection of any defects over the entire inspected area, it is currently necessary to correct for attenuation variations related to the different thicknesses traversed. This correction can be digital, through multi-gain testing, or physical, using a reference part.

[0166] In these cases, the invention makes it possible to reduce acquisition times by performing a single-gain acquisition but also to overcome the misleading indications caused by the differences between the production parts and the reference part.

Claims

Demands

1. A computer-implemented method for ultrasonic detection of air zone defects in a part to be inspected, the method comprising: - receiving an ultrasonic map of the part to be inspected; - receiving a thickness map of at least a portion of the part to be inspected; - determining, from the thickness map of at least a portion of the part to be inspected, a simulated ultrasonic map of at least a portion of a part without air zone defects having the same composition and the same thickness map as the at least a portion of the part to be inspected; - determining, from the ultrasonic map of the part to be inspected and the simulated ultrasonic map, a detection map of the part to be inspected;- determine, by applying a predefined threshold to the detection map of the part to be inspected, the presence or absence of an air zone type defect in the part to be inspected.;

2. A method according to claim 1, wherein the thickness map is a thickness map of the whole part, wherein the thickness map of the part to be checked comprises a plurality of pixels, each pixel of the plurality of pixels being associated with a respective value, wherein the simulated ultrasonic map is determined by applying a transformation to the pixel values ​​of the thickness map of the part to be checked.

3. A method according to claim 1, wherein the part to be inspected comprises a first part and a second part bonded together, the second part being manufactured according to a predefined digital model, wherein the thickness mapping is a thickness mapping of the first part of the part to be inspected before assembly with the second part of the part to be inspected, wherein the ultrasonic mapping of the part to be inspected is an ultrasonic mapping of the assembled part to be inspected, the method comprising in in addition: - receive a reference ultrasonic map of the second part of the part to be inspected, the reference ultrasonic map of the second part of the part to be inspected corresponding to an ultrasonic map of a second reference part manufactured from the predefined digital model and not including any air zone type defects; in which the simulated ultrasonic map is determined from the thickness map of the first part of the part to be inspected and the reference ultrasonic map of the second part of the part to be inspected.

4. A method according to claim 3, wherein the thickness map of the first part of the part to be inspected comprises a plurality of pixels, each pixel of the plurality of pixels being associated with a respective value, the method further comprising: - applying a transformation to the plurality of pixels of the thickness map of the first part of the part to be inspected; wherein the simulated ultrasonic map is determined from the reference ultrasonic map of the second part of the part to be inspected and the transformed thickness map of the first part of the part to be inspected.

5. A method according to any one of the preceding claims, wherein the detection mapping is obtained by subtracting the ultrasonic mapping of the part to be inspected from the simulated ultrasonic mapping.

6. A method according to any one of the preceding claims, wherein the part is an aeronautical part.

7. A method according to the preceding claim in combination with any one of claims 3 and 4, wherein the part is an engine blade, wherein the first part of the part is a metal leading edge, and wherein the second part of the part is a woven composite material body.

8. A method according to any one of the preceding claims, wherein the air zone type defect is the presence of a crack, fissure, delamination, or delamination.

9. Ultrasonic device for detecting air zone defects in a part to be inspected, the device comprising: - an input interface configured to: • receive an ultrasonic map of the part to be inspected; • receive a thickness map of at least a portion of the part to be inspected; - a circuit configured to: • determine, from the thickness map of at least a portion of the part to be inspected, a simulated ultrasonic map of at least a portion of a part without air zone defects having the same composition and thickness map as at least a portion of the part to be inspected; • determine, from the ultrasonic map of the part to be inspected and the simulated ultrasonic map, a detection map of the part to be inspected;• determine, by applying a predefined threshold to the detection mapping of the part to be inspected, the presence or absence of an air zone type defect in the part to be inspected.

10. Product computer program comprising instructions to implement the method according to any one of claims 1 to 8 when this program is executed by a processor.

Images